METALLIC SOLUTIONS. 29 



juice in which the tissue is left five minutes. Then it is soaked 

 for 15 to 20 minutes in 3 c.c. of a one per cent, solution of the 

 gold chloride, and finally 25 to 30 minutes in distilled water 

 to which one or two drops of acetic acid has been added. After 

 two or three days' exposure to the sun, the fibres become dis- 

 tinct. 



Nitrate of silver in solution (gr. j. iv. j.) is much used. 

 The details of the method will be found in the Chapter on the 

 Lymphatics. 



Chloride of gold has also been much used in studying 

 the so-called lymph-canalicular system of the cornea. The 

 method of employing it will be found in the section relating to 

 the cornea. 



Osmic acid in solution is also very useful. Its effects are 

 given in the chapter on the General Histology of the Nervous 

 System. 



Methyl-green for showing waxy change. Curschmann, of 

 Hamburg, has recommended this reagent to effect the same 

 object as the molet de Paris of Cornil. A solution of about 

 five grains to the ounce is used. The specimens are bathed in 

 the fluid a few minutes or hours. They take the color quickly. 

 After staining they may be mounted in glycerine. The amy- 

 loid material assumes a brilliant rose color. The surrounding 

 tissue takes a dull green. 



Wicliersheimer's preserving liquid. This material has 

 been extensively used of late, and there are several formulae 

 for it. Among the most recent modifications is that made by 

 the firm of Poetz & Flohr, of Berlin. For immersing speci- 

 mens the ingredients are : arsenious acid, 12 grains ; sodium 

 chloride, 60 grains ; potassium sulphate, 150 grains ; potassium 

 nitrate, 18 grains; potassium carbonate, 15 grains; water, 10 

 litres ; glycerine, 4 litres ; wood naphtha, i litre. A modified 

 fluid is used for injecting the blood-vessels. This is suitable for 

 all fresh tissues, preserving them in their natural color and 

 consistence. 



If the tissues are to be used subsequently for the micro- 

 scope, it is said that they should be washed thoroughly in 

 water, but it seems from recent experiments that the fluid un- 

 fits them for minute examination. It is also rather expensive, 

 and has an extremely pungent and unpleasant odor. 



